The detection of stress has numerous applications in the security field. For example, in airports, it would be desirable to measure or detect stress of individuals that have been singled out and will be interviewed. Military applications include interviewing suspected terrorists in fixed facilities and in remote locations. In other instances, stress can be an indication of untruthfulness. Thus, for example, the detection of stress can be useful during police interrogations as an indicator of untruthfulness. In addition, the detection of stress can be used by parole boards to help determine stress levels when addressing certain topics that would be sensitive to the reason for the incarceration of the individual. The detection of stress in the corporate world can be useful when interviewing personal for sensitive job positions in high security applications.
In general, the detection of stress in a subject involves invasive techniques, where a device needs to be physically attached to the subject. With security applications, invasive techniques are impractical and offer little value. Thus, it would be desirable to detect stress levels in a subject without the subject knowing he is being examined. One approach is to measure the skin temperature of the subject. U.S. Pat. No. 5,771,261 to Anbar describes how dynamic area telethermometry (DAT) can be used to detect changes in skin temperature and skin perfusion and subsequently correlate the changes to mental stress. Thus, the use of infrared cameras to measure changes in a subject's skin temperature during police interrogations can be an indication of whether or not the subject is being honest when responding to questions.
Although the use of infrared cameras provides useful information about the stress level of a subject, the results in the absence of other data can be misleading. For example, changes in temperature in a police interrogation room may result in an increase in skin temperature. Further, prolonged interrogations can also provide a steady increase in skin temperature. Thus, what is needed is a device that can simultaneously measure or detect a plurality of stress indicators in a subject. For example, by simultaneously measuring or detecting changes in several features of the subject, it is possible to more reliably determine whether or not the subject is being truthful. Described herein are stress detection devices and methods of using thereof that overcome the limitations of previous stress detection devices.